MDL has redeveloped Eta MOS guidance using a high-resolution archive in space and time. We are planning to implement several changes to the system in two stages. The tables below list the changes for the two implentations, and details follow.

Changes in the Second Implementation - Effective February 24, 2004

Eta MOS Available for Additional Sites Including Alaska

MDL will make changes to the stations that are available in the Eta MOS products. Guidance for sites in Alaska and Hawaii will now be available, and 142 new sites in the CONUS will be added to the MET text messages. The complete list of WMO and AWIPS headers for the Eta MOS MET text bulletins are as follows:

Eta MOS MET Text Messages Extended to 72 hours

The format of the Eta MOS MET text messages will be modified to allow for guidance out to 72 hours in advance. At this time, we will change the format of the text products to allow for guidance at 66 and 72 hours, but we will not be adding those forecasts, due to the current timing of the Eta model run. In early April, NCEP will be making changes to the Eta model run times, and then we will add the 66- and 72-h guidance to the messages with much less impact on delivery time. At this time, we will fill the 66- and 72-h positions with the appropriate missing indicators.
Sample 0000 and 1200 UTC MET messages with new elements out to 72 hours are available athttp://www.nws.noaa.gov/mdl/synop/tin/eta32.htm

New Total Sky Categories

The definition of categories of total sky cover will be modified to distinguish between FEW and SCATTERED clouds. The new categories are as follows:

Addition of Snowfall Amount and Ceiling Height Guidance

Categorical forecasts of snowfall amount will be available in the Eta MOS text products for 24-h periods ending at approximately 36 and 60 hours after 0000 UTC (60-h forecast not available until April); and 24, 48, and 72 hours after 1200 UTC (72-h forecast not available until April). Snowfall amount forecasts will be available from September 1 through May 31 for most sites in the MOS system. The snowfall amount categories are as follows:

Categorical forecasts of ceiling height will be available in the Eta MOS text products. These categories are not the same as those in the current GFS MOS. An additional category has been added to distinguish between 1000 - 1900 ft and 2000 - 3000 ft. The ceiling height categories are as follows: